The present invention relates an apparatus for automatically composing a music piece.
One of the important considerations of an automatic composer is that the automatic composer in question is capable of composing a music piece familiar to a human i.e. not merely mechanical but full of musicality.
For example, U.S. Pat. No. 4,339,731 issued to E. Aoki on Aug. 23, 1983 discloses an automatic composer comprising means for randomly sampling individual pitch data from a set of pitch data such as a twelve note scale data and means for checking whether the sampled data satisfies limited musical conditions. When the sample satisfies the conditions, it will be accepted as a melody note. If not, the sample is rejected as a melody note and a new sample is taken out for further checking. Accordingly, the basic process by this automatic composer is a trial and error. At the stage where pitch data are randomly sampled, they constitute a totally disordered sequence of pitches, which is remotest from good music: a chance of obtaining a melodic piece would be negligible; as low as once in an astronomical number of times. Hence, the above apparatus provides means for checking sampled data as to their musical conditions, or selecting data by means of a condition filter. The selection standard is, therefore, a key factor. If the selection were too restrictive, generated melodies would lack in variety. If the selection were too wide, the original disorder would be predominant in the melodies generated.
The above-mentioned automatic composer is more suitable for generating a melody remote from any existing music style rather than one familiar to a human, and is primarily useful for music dictation i.e. solfeggio and/or performance exercise, because novel or unfamiliar music is difficult to read or play. The above automatic composer lacks, therefore, in the ability as mentioned at the beginning.
Other techniques of automatic composition are disclosed in USP 4,664,010 to A. Sestero, May 12, 1987 and WO 86/05616 by G. B. Mazzola et. al. Sept. 25, 1986. The former patent relates to a technique of converting a given melody into a different melody by performing a mirror or symmetry transformation of given melody with respect to particular pitches. According to the latter patent application, a given melody is graphically represented by a set of locations in a two dimensional space having a pitch axis (Y axis) and a time axis (X axis). A suitable transformation is carried out over the given melody with respect to the two axis, thus developing a new melody formed with a sequence of pitches and a sequence of tone durations.
Either of the above techniques only employs mathematical transformations such as a symmetry conversion, and cannot be said to contemplate musical properties of melody; thus, the chance of achieving good music compositions would be relatively low as compared to the present invention.
Another automatic composer is disclosed in Japanese Patent laid open (Kokai) 62-187876 by the present inventor, Aug. 17, 1987. This apparatus comprises a table representing frequencies of pitch transitions and a random number generator. In operation, tone pitches are successively developed from the outputs of the frequency table and the random number generator to form a melody. The frequency table makes it possible to compose music which accords with the musical style designated by a user. Even this arrangement cannot be said, however to do analysis and evaluation of musical properties of melody for music composition.
Other relevant techniques are disclosed in USP 3,889,568 issued June 17, 1978 concerning a system of chord progression programs, Japanese patent laid open (Kokai) 58-87593, May 25, 1983 and U.S. Pat. No. 4,539,882, Sept. 10, 1985 concerning an apparatus for automatically assigning chords to a melodic line.
An automatic composer solving the problems in the prior techniques cited above has been recently proposed by the present inventor (U. S. patent application Ser. No. 177,592, filed on Apr. 4, 1988). The automatic composer comprises a melody analyzer means for analyzing a melody (motif) provided by a user and a melody synthesizer for synthesizing a melody from a given chord progression and the result of the melody analysis. The melody analyzer includes nonharmonic tone classifying means for classifying nonharmonic tones contained in the input melody. The melody synthesizer has an arpeggio generator for generating arpeggio tones in accordance with the chord progression and nonharmonic tone adding means for adding nonharmonic tones to the generated arpeggio tones. Therefore, the features of the melody (motif) input by the user are expanded in the melody generated by the automatic composer. In addition, the automatic composer regards a melody as a row of harmonic tones mixed with nonharmonic tones: First, the arpeggio generator completes a succession of tones consisting of only harmonic tones. Then, the nonharmonic tone addition means combines nonharmonic tones with the succession of harmonic tones, thus completing a melodic line. This approach increases the chance of obtaining a good music piece.
However, the automatic composer still leaves room for improvement which is the primary object of the present invention. Disadvantages of the automatic composer are:
(a) a synthesized melodic line following the input melody tends to deviate from the input melody because of incomplete reversibility between the melody analysis and the melody synthesis;
(b) interaction between the hierarchic structure in melody and that in chord progression is ignored;
(c) because the musical knowledge applied in the automatic composer is permanently built in the system, the knowledge is difficult to change; and
(d) tonality of music can be deceived or vague because there is no means preventing the melody synthesizer from using a tone other than scale notes.